A sensitive high resolution zone electrophoretic system developed in our lab was used to evaluate the plasma lipoproteins of untreated patients with type-2a hyperlipoproteinemia. Five distinctly different electrophoretic patterns were observed. Unique clinical features were correlated with electrophoretic patterns. The electrophoretic heterogeneity found in these patients supports the concept that the type-2a phenotype includes several molecular defects which are not detectable by quantitative methods of analysis (1).